Effect of Calcium Sulphate on the Geotechnical Properties of Stabilized Clayey Soils

An experimental investigation was undertaken to study the effect of calcium sulphate (CaSO4.2H2O) on the behaviour of the grey clay (GS) and red clay (RS) soils stabilized with lime (L), natural pozzolana (NP) and their combination (L-NP). In this study, the geotechnical properties investigated are respectively, the Atterberg limits on samples cured for 1 to 30 days to assess the diffusion time effect of CaSO4.2H2O (DTC) in the soil paste and the unconfined compressive strength (UCS) on samples cured for 7 to 120 days. The results show that both GS and RS samples can be successfully stabilized with L alone or with L-NP which substantially reduce their plasticity index (PI) and increase their UCS. On the other hand, a negligible effect was reported when the NP is used alone. However, when combining a fraction of CaSO4.2H2O to samples containing L or L-NP, a further decrease in the PI is observed. In addition, higher UCS values are recorded.